Non contact volt meters are well known in the art. A typical non contact volt meter comprises a hand held package which includes a field sensing arrangement and a volt meter display operative to move a pointer to a voltage value representative of the field sensed.
Such a meter employs a capacitive sensor. The capacitor is exposed to a test object through a metallic layer which includes an aperture aligned with the capacitor. The time constant characteristic of the sensing electronics in such a meter is such that the frequency of operation is too low for many desirable applications.
In order to improve the frequency of operation, such meters are adapted to vary the separation between the test object and the sensor which, in fact, constitutes the two plates of the capacitor. This variation is implemented by fixing the sensor to a tuning fork. Frequencies on the order of one hundred Hertz are achieved in this manner. But such frequencies are still much lower than those required, for example, for sensing the voltage or charge on an electrostatic belt or drum typical of photocopy equipment.
Such meters, further, are quite bulky. Many potential uses for non contact volt meters allow little space for such equipment. A high speed and small non contact volt meter would find an eager market for many applications.